I'm sensing a lot of hostility from you. I am engaging you in discussion in a respectful manner, and I expect a decent amount of reciprocation.

Not once have I said that this is a certain solution. I proposed it as a potential solution that we can discuss, like adults. Usually this takes the form of one person advocating, and the other critiquing it. It appears that the two of us fill these roles nicely.

The end result is that people can hopefully learn something. It may well turn out that this idea is worthless, but the only way to find out is to explore it. If it does indeed turn out to be worthless, then at least we've learned something. And if it turns out to be fruitful, then there is value in that too.

I'm off to dinner, will look into your response when I get back.

peace.

p.s. i will respond to one point for now: the resolution of the wavelength scale is not necessarily an issue, if all you are interested is in chromaticity.

Those pen-ray lamps are perfectly fine for checking the wavelength calibration of a spectrometer, I use them for this purpose all the time. They cannot however tell you whether the radiometric calibration has drifted, you need absolute standards for that. Absolute standards and the knowledge of how to use them properly is typically very expensive.

the lamp needs a power supply/conditioner to have stable output, they using air cooling for the lamp to be stable also...

Thats correct. The power supply/conditioner costs $263.

Quote:

Originally Posted by zoyd

Those pen-ray lamps are perfectly fine for checking the wavelength calibration of a spectrometer, I use them for this purpose all the time. They cannot however tell you whether the radiometric calibration has drifted, you need absolute standards for that. Absolute standards and the knowledge of how to use them properly is typically very expensive.

Thanks zoyd. That makes perfect sense. You can use the known spectral lines of mercury/argon to verify your meter is reading wavelengths correctly. Jeti even suggests using a typical florescent lamp to do so. Of course, you can't tell if the absolute levels are correct.

In your experience, have you found spectroradiometers to materially drift with age? If they have, have they drifted in wavelength or absolute luminance?

do you have chromaticity measurements of that lamp? you need these data to compare your meter with the lamp to see if it reads well.

I'm pretty sure any company that sold lamps that included spectral data would also include chromaticity data. You could always ask for it if they didn't by default. And if they only provide spectral data, it's a relatively trivial step to derive chromaticity from spectral data. I've written code in matlab that does exactly this. All you need is the value at each wavelength, and then you feed it into the standard observer color matching functions and you have your X Y Z.

I'm pretty sure any company that sold lamps that included spectral data would also include chromaticity data. You could always ask for it if they didn't by default. And if they only provide spectral data, it's a relatively trivial step to derive chromaticity from spectral data. I've written code in matlab that does exactly this. All you need is the value at each wavelength, and then you feed it into the standard observer color matching functions and you have your X Y Z.

Companies that sell lamps include spectral data, but its not even necessary for them to do so. Mercury is mercury. Argon is argon. Their spectra is well defined from basic physics. I'm not sure why you even need the chromaticity when you have spectral data. Spectral data is of course a fuller and more robust description of the light source then "summary statistics" such as chromacity or CRi.

What I don't know is how to access the spectral density of an observed light source from an i1pro. Specifically, is there software that will interface to an i1pro and produce a spectral graph of a measured light source?

Companies that sell lamps include spectral data, but its not even necessary for them to do so. Mercury is mercury. Argon is argon. Their spectra is well defined from basic physics. I'm not sure why you even need the chromaticity when you have spectral data. Spectral data is of course a fuller and more robust description of the light source then "summary statistics" such as chromacity or CRi.

Yep, unless you can't access the SPD of your own measurements directly, in which case a chromaticity reference would have to be the next best thing.

Quote:

Originally Posted by work permit

What I don't know is how to access the spectral density of an observed light source from an i1pro. Specifically, is there software that will interface to an i1pro and produce a spectral graph of a measured light source?

I could have sworn that HCFR outputs a spectral power distribution graph - I'm setting up my i1pro again this wknd to compare the primaries from two trinitrons. Will keep an eye out for the SPD graph

well the optical resolution (spectral resolution) of the i1 pro is 10nm, which is the resolution of that HCFR graph. HCFR does provide a high resolution mode, where you can use the 3.5 nm sampling resolution that the instrument is capable of (sampling resolution refers to the distance between each detector in the detector array).

My understanding is as follows (and I'm still trying to piece this all together):

the higher sampling resolution will not reveal any higher resolution spectral data, but will rather only provide you with a higher resolution view of the instruments response to that part of the spectrum.

For example, if you have a monochromatic source at 500nm, the instrument will not respond with a perfect spike. Rather, it will have a particular shape to it (I think this is the bandpass function). For array type instruments, I believe the shape is somewhat Gaussian. If you sample along this bell shaped curve, you'll get more information about the bandpass function of the instrument, but it would be misleading to suppose that these data points reflect a Gaussian spectral source.

However, there may be dividends from this approach, in the context of deriving chromaticity.

On the other hand, there may also be some downsides to using a mismatched sampling vs. spectral resolution - I believe when measuring emission lines, a mismatch between these two parameters can introduce errors. I think this is only the case with mechanically based instruments, and an array based instrument like the i1pro may not suffer this problem.

Just found this page, haven't read it yet, but it looks like it deals with this issue:

While this is interesting from a theoretical stand point it's not really relevant to the OP who I am assuming is not going to start a research project to check his i1pro. He actually answered his own question best:

Quote:

Couldn't another amateur with a recently certified reference meter be able to compare the two and tell me how accurate my meter is?

yes, this is your best low (no) - cost alternative and yes if it is found to have an offset you can calculate a correction matrix for it. For non-professional use this is a perfectly appropriate option.

In general spectrometer wavelength registration will not drift over time any appreciable amount as long as they don't experience any physical shocks (either through actually dropping one or extreme temperatures). Changes in throughput will occur over long periods of time as the coatings on the optical components age and this is dependent on how the device is handled and stored. A well maintained unit can stay in-spec for many years but not knowing it's history it would be a good idea to cross-check it with someone who has a fresh unit.

For a quick and easy spectral check you can measure a garden variety compact fluorescent with the 1pro in high sampling mode using ArgyllCMS (similar output is available in HCFR)

And either eyeball or do a gaussian centroid of the peaks and verify locations using the reference peak locations used for these measurements.

In the data above the 2nd peak eyeball fit is 436 nm, the Hg emission line for that peak is at 435.83 nm.

Here is the same data using HCFR:

The green peak is straddled by 543.33 nm and 546.67 nm [reference Hg line is 546.047 nm]
The red peak is straddled by 610.0 nm and 613.33 nm [reference europium peak is at 611 nm]

It's easier to send yor meter to SpectraCAL from doing all this DIY calibration lamb thing at home. From all these years im reading various forums, I haven't seen a single person who has a calibration lamp at his home.

* Don't forget the people here at this topic have asked for a cheaper solution of check some 2nd hand old meters.

Sorry to break this to you, but have you looked at yourself in the mirror lately?

"All new diagnostics and self-correction features Wavelength calibration LED allows for self diagnosis of optical grating in relation to sensor during white calibration (with automatic correction and notifications) - See more at: http://blog.xritephoto.com/?p=8177#sthash.HbWZcSGV.dpuf"

It's easier to send yor meter to SpectraCAL from doing all this DIY calibration lamb thing at home. From all these years im reading various forums, I haven't seen a single person who has a calibration lamp at his home.

* Don't forget the people here at this topic have asked for a cheaper solution of check some 2nd hand old meters.

Sorry to break this to you, but have you looked at yourself in the mirror lately?

"All new diagnostics and self-correction features Wavelength calibration LED allows for self diagnosis of optical grating in relation to sensor during white calibration (with automatic correction and notifications) - See more at: http://blog.xritephoto.com/?p=8177#sthash.HbWZcSGV.dpuf"

For i1PRO2 you are talking about, the topic has to do with 5-10 year old 2nd hand i1PRO1 meters.

What do your mean by this? someone with a LED source can check it's meter at home?

If you need answers to your scientific discoveries, please talk directly with the Lab Director of a NIST Lab to give you all the answers, to tell you exactly why all that lamp/led ideas are truly waste of time for home use from a calibration hobbyst user.

AGAIN...the topic here is help someone to find a cheaper way to check his meter, cheaper from 175$ of SpectaCAL's NIST Certificated Lad check of the meter performance.

a colorimeter does not measure the spectral power distribution of a light source - it uses filters that try to approximate the standard observer color matching function. A colorimeter can only give chromaticity. A spectro measures the output at each wavelength, and can derive chromaticity directly from that data.

well, if you have a reference source whose chromaticity you know, you can measure it with your colorimeter and check the chromaticity readings. But keep in mind that with a colorimeter, you have the added issue of accuracy being dependent upon spectral source.

I'd reckon that your best bet with a colorimeter is to profile it against a spectro for the display you're measuring. What instrument are you concerned about?